Apatite ore formation

Magnetite-apatite ores of Kovdor deposit have been formed completely other way. It deposited among igneous or, in other words, magmatic rocks. The geologists established that magma outbreak took place from the deep earth to the surface in several site of the Kola North about 350-400 million years ago. Molten magma was moving by channel resembling pipe by portions, pulsing. Each time it was magma of different composition coming out on surface, therefore, during its cooling down different rocks were formed including magnetite-apatite ores. Ore beds as if were rolled are presented in the geological maps as arches, sometimes almost closed annular bands.

Kovdor iron ore deposit can be compared to nail that broke through the Earth crust, this iron nail has length of several kilometers, thickness of 0.5 kilometer, nail-head on the surface of up to 1.5 kilometer. Besides magnetite-apatite ores, Kovdor massif of igneous rocks has several mica deposits - vermiculite, phlogopite and staffelite - variety of apatite. However, time and conditions of its formation are different. Concentration of valuable minerals is connected to long weathering rather than magmatic activity. Carbonate rocks with apatite inclusions are common for Kovdor massif. Calcium and magnesium carbonates - calcite and dolomite are dissolved and taken by water coming to the surface, but apatite being chemically-resistant mineral stays as it is and accumulates. Lower surface of staffelite deposit or as geologists say, bottom has an inhomogeneous shape with many benches and depressions or pockets filled with ore.

Phlogopite and vermiculite deposits are formed during weathering under thermal water exposure on specific rock - pegmatite consisting of large crystals of olivine and diopside, that is iron, magnesium and calcium silicates of 1-2 m in size. In some individual cases - 10-15 meters long. During complicated natural chemical reactions the mineral composition being part of pegmatite nest body is changing - it results in simple silicate as olivine and diopside transformation into hydromica - phlogopite, vermiculite.

Apatite-nepheline ore is mined in the Khibiny more than half a century and same amount of time is dedicated to scientific disputes and discussions on issues of its origin. There are many questions: where phosphate comes from to form such a large apatite deposits while its content is minor in the Earth crust? Why apatite deposits can be found only in the Khibiny and can it be found somewhere else? To obtain success one need to give correct answers.

Apatite-nepheline ores that composed bed deposits among unusual rocks are rich in nepheline – aluminum, sodium and potash silicates. Such rocks are rare in the world, apatite deposits can’t be found anywhere except the Khibiny. If one knows the reserves of apatite-nepheline ores as well as phosphate content in adjoining rocks it easy to evaluate what amount of this element is located in ore bodies and what is dispersed in the rockmass. It turned out that the nature is lavish: only 1/10 of phosphate in ore was used for deposit formation. Therefore, the answer to first question is simple: phosphate amount in magmatic melt was enough to form thick deposits of rich phosphate ores.